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Jon Elson

wrote:

My old inverter worked flawlessly. It's rated at 300 watts (Peak), which
means it's really 150 or 200W. A local second hand store had a 400W
(RMS) inverter. The store owner said he's not sure if it works, and he
told me to take it out to my car and plug it in. I plugged it in, and
the moment I turned on it's power switch, it blew the 15A fuse to the
cig lighter in my car. (Nothing was plugged into the 110VAC output).

The store owner knows me, and he told me to take it home and see if I
can get it to work, and if it does, give him $5, if not, just bring it
back. I put a multimeter across the 12V input leads, and get around 500
ohms, which rises over time. I opened it up, and found it has a 25A
built in fuse. This makes me wonder if it requires 25A to work, even
with no load?????

400 W requires 33.33 A at 100% efficiency. So, it could not possibly be a
400 W inverter. But, maybe 400 W peak, for a very short peak.
My question is this: How much current is required for these inverters,
depending on their wattage rating? I have never seen any of them with
the required input amperage listed on them?

While looking on ebay, I noticed a lot of then rated at 2000, 4000, and
even higher wattage. In fact I saw one listed at 16,000 watts.
16 KW? That will need 1333 A at 100% efficiency. No WAY would anyone ever
build a 16 KW inverter that ran off 12 V DC. More like 120 V DC input.

Obviously
these high powered ones need to be hard wired to the car battery (not
using the cig lighter socket), but I can not see how any car battery or
alternator could handle a 16,000 watt unit.

I had no luck looking for a website that shows the rated input amps for
inverters, based on their output power.
You don't NEED a web site! Watts / V = current! VERY simple calculation,
(when ignoring efficiency.)

Jon